Inorganic salt removal from oil-soluble sulfonates



March 31, 1959 VOL. SEDIMENT J.. M. HONEYCUTT 2,880,173

INORGANIC SALT REMOVAL FROM OIL-SOLUBLE SULFONATES Filed April 10, 1957SEDIMENT VS. ACETONE FOR VARIOUS SULFONATE 0.5 o-eam m I I% s m LEGENDSULFONATE' COAGULANT MIXTURE 50% 50% 30% 70% 75% |s% 82% lo% 90% -TWOPHASES BEYOND THESE P 2o so To ACETONE IN COAGULANT MIXTURE Jerald M.Honeycufl Inventor United States Patent O INORGANIC SALT REMOVAL FROMOIL-SOLUBLE SULFONATES Jerald M. Honeycutt, Bellaire, Tex., assignor toEsso Research and Engineering Company, a corporation of DelawareApplication April 10, 1957, Serial No. 652,059

'8 Claims. (Cl. 252-33) This invention relates to the removal ofinorganic salts from oil-soluble sulfonate detergents. Morespecifically, this invention pertains to the removal of inorganic saltssuch as sodium chloride from alkaline earth metal, especiallyoil-soluble calcium and barium soaps of sulfonic acids.

Oil-soluble alkaline earth metal sulfonates are today conventionallyemployed as detergent additives for lubricating oils and especially formotor oils. While there are many other uses for these sulfonates, suchas emulsifiers and as thickeners in greases, this invention will findits greatest applicability in the treatment of motor oil detergentadditives.

The sulfonates with which this invention is mainly concerned are theoil-soluble soaps of alkaryl sulfonic acids, such as mahogany acidsproduced during the treatment of lubricating oil distillates withconcentrated to fuming sulfuric acid and synthetic sulfonates producedby the sulfonation of certain hydrocarbons. These sulfonic acids may berepresented by the following structural formula:

where R is one or more alkyl, alkaryl or aralkyl groups and the nucleusmay be a single or condensed aromatic ring or a partially hydrogenatedring. The alkyl radicals will generally contain a total of from 17 to 36carbon atoms per sulfonic molecule.

While the sulfonic acids synthetically produced are generally mixturesof compounds having various molecular weights, typical of these acidsare dinonyl naphthalene sulfonic acid, didodecyl benzene sulfonic acid,and mixtures of monoand di-tetrapropyl benzene sulfonic acids. Themolecular weight of the sulfonic acids may vary between 350 to 600 andpreferably will average about 400 to 560. Occasionally slightly lowermolecular weight compounds are employed together with higher molecularweight sulfonic acids. Apparently the characteristics of the highermolecular weight acids are sufiicient to solubilize the lower molecularweight compounds which normally by themselves would not have thenecessary degree of oil solubility. In the formation of these acids frompetroleum fractions the lower molecular weight compounds which arewater-soluble are usually extracted from the acid treated oil by theaddition of water. The more desirable high molecular weight oil-solubleacids are normally recovered as sodium or alkali metal soaps byneutralization with sodium carbonate or other alkali metal base followedby extraction with aqueous alcohol. Sodium carbonate, sulfate, sulfiteand the like are first removed and the remaining sodium sulfonate isthen generally diluted with a light lubricating oil, e.g. a parafiinicor napthenic oil having a viscosity between 40 and 60 S.U.S., to yieldgenerally about a 30 to 70 wt. percent sodium sulfonate concentrate. Thealkyl aryl sulfonic ice acids prepared by sulfonation of the alkylbenzene or the like are converted to the alkali metal salt in a similarmanner.

To prepare the alkaline earth metal salts these sodium sulfonates arereacted with calcium or other alkaline earth metal chloride to effect adouble decomposition type reaction. While other methods for thepreparation of the calcium sulfonate are known the above methods havebeen found to be most attractive from an economic standpoint.

One of the primary difliculties in the preparation of calcium sulfonatesby the above described processes is that sodium chloride, sodium sulfateor other inorganic salt is held in the alkaline earth metal sulfonatesolution apparently in the form of a relatively stable colloidalsuspension. Water washing and other conventional techniques for theremoval of water-soluble salts were tried but were found ineffective forremoving substantial portions of the salt. The salt is undesirablebecause it forms hazy solutions when the sulfonate is blended withmineral oils and even causes precipitates to form when the oils containother detergents and detergent inhibitors.

It has now been found that a calcium sulfonate con- I taining inorganicsalt may be treated with a composition comprising a specific coagulantsuch as a low molecular weight ketone, e.g. acetone, and methyl ethylketone, or isopropyl alcohol or the like in an organic solubilizercomprising petroleum naphtha, petroleum ether, narrow cut naphthas,hexane, heptane, octane and the like, to effectively remove theinorganic salt contaminants therefrom. Of the above coagulants acetonehas been found to give the best results. It has been further found thatthe particular treatment employed is so effective and reliable whencontrolled that it is suitable for use as an analytical or control testfor product purity. In general the process of this invention comprisestreatment of the inorganic salt contaminated calcium sulfonate with certain mixtures of coagulant in solubilizer. From the thus treatedsulfonate the sediment may be removed by any conventional means,especially preferred being centrifugation, filtration, settling anddecanting and the like. While the acetone to solubilizer ratio will varywith the amount of calcium sulfonate employed, to eflect relativelycomplete salt removal homogeneity in the system must be maintained sincethis desalting process fails if the system becomes two-phased. On theother hand, if too little coagulant is added a haze is formed and thesediment or precipitate which occurs is in a fluid rather than solidform, indicating that some of the concentrate mixture is entrained inthe salt. Thus if the sediment flows as a fluid the amount of saltprecipitated cannot be determined accurately. Further in precipitatingthe salt as a fluid some of the organic product is lost, thus making theprocess less economically attractive for commercial scale operations.

For ease of discussion the term sulfonate concentration as employedherein means the weight percent of alkaline earth sulfonate in thesulfonate concentrate. The term coagulant refers to acetone, methylethyl ketone, isopropyl alcohol and the like, and coagulant mixturemeans the coagulant plus the solubilizer.

The sulfonate concentration is not critical and may vary from 30 to 70%.The criticality relates to the ratio of sulfonate to the coagulantmixture and to the ratio of coagulant to solubilizer.

Several tests were carried out employing a 30 wt. percent concentratecalcium sulfonate in a solvent refined and clay contacted lubricatingnaphthenic oil having a viscosity of about 40 S.U.S. The sulfonate wasprepared by sulfonating a polypropyl benzene fraction boiling in therange of about 650 to 800 F., forming the sodium soap of the sulfonicacids and then converting the sodium sulfonate to the calcium sulfonateby double decomposition with calcium chloride. The sulfonic acids had anaverage molecular weight of about 415. Acetone was employed as thecoagulant and hexane as the solubilizer. The results are shown in thefollowing table and depicted in graph form in the drawing.

Table 2. A method of removing entrapped inorganic alkali metal saltcontaminants from an oil-soluble alkaline earth metal sulfonateconcentrate, previously prepared from alkali metal sulfonate, whichcomprises admixing therewith a composition comprising a low molecularweight ketone and a hydrocarbon solubilizer in an amount sufii- Vol.Percent of Vol. Per- Sulfonate cent Coneen- Coagulant trate 1 Mixturecoagulant Mixture Percent Dry Soap cent Acecent Solutone bilizer Vol.Per- VoLPercent Sedi- State of Sediment l 7.5 75 l i Flows.

Solid.

Flows.

0. Solid.

Flows.

D Solid.

Flows. Do. Do. Solid.

Flows. Do.

Solid.

Flows. D Do.

1 Containing wt. percent sulfonate. 3 Based on coagulant mixture 3Initial sediment after centrifuging/sediment obtained after a 24-hourperiod.

In the above tests the defined quantities of coagulant mixture wereadmixed with the defined quantities of sulfonate concentrate at roomtemperature. The mixtures were then immediately centrifuged andrecentrifuged after a 24 hour period.

Those tests wherein the sediment occurred in fluid form are inoperativefor the purposes of this invention since the amount of salt obtained cannot be determined from the volume of sediment. Also substantial loss ofdetergent product would be realized. Where two phases formedsubstantially no sedimentation occurred.

The above tests show that high volume ratios of coagulant mixture to the30% sulfonate concentrate in the range of about 9/1 to 2/1 are necessaryfor the removal of substantial amounts of salt. Within these ranges,however, it is also necessary to maintain specific ratios of coagulantto solubilizer ranging from 1:1 for the larger volumes of sulfonateconcentrate to about 3:1 for the smaller volumes of sulfonateconcentrate, e.g. 10 vol. percent. More accurately these ratios can beexpressed as based on dry soap, i.e. the volume percent of sulfonate inthe sulfonate concentrate. Thus the ratio of coagulant mixture to drysoap would be from about 30/1 to 7/1, the ratio of coagulant tosolubilizer being as noted above.

What is claimed is:

1. A method of removing entrapped inorganic alkali metal saltcontaminants from an oil-soluble alkaline earth metal sulfonate,previously prepared from alkali metal sulfonate, which comprisesadmixing therewith a composition comprising a coagulant selected from agroup consisting of alcohols and ketones and a hydrocarbon solubilizerin an amount sufiicient to form a relatively clear solution andinsufficient to result in two liquid phases, precipitating in the formof a solid sediment said salt contaminants and removing saidcontaminants from said solution of the sulfonate.

cient to form a relatively clear solution and insuflicient to result intwo liquid phases, precipitating in the form of a solidsediment saidsalt contaminants and removing said contaminants from said solution ofthe sulfonate concentrate.

3. A method of removing entrapped inorganic sodium salts from anoil-soluble calcium sulfonate, previously prepared from alkali metalsulfonate, contaminated therewith, which comprises adding to saidcontaminated calcium sulfonate acetone and a hydrocarbon solubilizer inan amount sufficient to form a relatively clear solution andinsuificient to result in two liquid phases, contrifuging the totalmixture to precipitate in the form of a solid sediment said saltcontaminants and removing said contaminants from said solution of thecalcium sulfonate.

4. A process for the removal of entrapped inorganic sodium saltcontaminants from an oil-soluble calcium sulfonate concentrate,previously prepared from alkali metal sulfonate, which comprisesadmixing with said concentrate a coagulant hydrocarbon solubilizermixture, wherein said coagulant is selected from a group consisting ofalcohols and ketones in the volume ratio of 30/1 to 7/1 of said mixtureto calcium sulfonate, said mixture having a solubilizer to coagulantvolume ratio of about 1/1 to 3/1 precipitating in the form of a solidsediment said salt contaminants and removing said contaminants from saidconcentrate.

5. A method in accordance with claim 4 wherein said coagulant isacetone.

6. A method in accordance with claim 4 wherein said coagulant is methylethyl ketone.

7. A method in accordance with claim 4 wherein said coagulant isisopropyl alcohol.

8. A process for the removal of entrapped sodium chloride from calciumsulfonate in a lubricating oil, said sulfonate having been previouslyprepared from an alkali metal sulfonate, which comprises admixingtherewith References Cited in the file of this patent acetone as acoagulant and hexane as a solubilizer in an amount suificient to form arelatively clear solution and UNITFD STATES PATENTS insufiicient toresult in two liquid phases, precipitating in 2,373,793 Susle Apr. 17,1945 the form of solid sediment the sodium chloride and re- 5 2,713,035Clarke July 12, 1955 moving the sediment from said solution. 2,738,326Alldfirson e a1 1955

1. A METHOD OF REMOVING ENTRAPPED INORGANIC ALKALI METAL SALTCONTAMINANTS FROM AN OIL-SOLUBLE ALKALINE EARTH METAL SULFONATE,PREVIOUSLY PREPARED FROM ALKALI METAL SULFONATE, WHICH COMPRISESADMIXING THEREWITH A COMPOSITION COMPRISING A COAGULANT SELECTED FROM AGROUP CONSITING OF ALCOHOLS AND KETONES AND HYDROCARBON SOLUBILIZER INAN AMOUNT SUFFICIENT TO FORM A RELATIVELY CLEAR SOLUTION ANDINSUFFICIENT TO RESULT IN TWO LIQUID PHASES, PRECIPITATING IN THE FORMOF A SOLID SEDIMENT SAID SALT CONTAMINANTS AND REMOVING SAIDCONTAMINANTS FROM SAID SOLUTION OF THE SULFONATE.